Diabetes, obesity and metabolic disease have reached epidemic proportions. Much research on these diseases has focused on tissues such as adipose, liver, muscle and pancreas. The role of the gut in glucose metabolism is relatively unstudied; however, it can also have a significant effect on systemic glucose control. Residing in the gut is a complex community of microbes, termed microbiota, which are important contributors to immunity and metabolism, frequently mediating cross-talks between these two functions. Changes in the gut microbiota of type 2 diabetes (T2D) patients are directly linked to metabolic dysregulation in the disease. Although multiple microbes have been suggested to be involved in this process, Akkermansia muciniphila has emerged in the literature most strikingly, with studies reporting its protective effect against metabolic abnormalities in mice and negative correlation with obesity in humans. Adaptive immunity, and in particular interferon-gamma (IFN?), is a major regulator of A. muciniphila levels in the gut, according to our preliminary results. Besides of its central role in antibacterial immunity, IFN? has been previously shown to have negative impact on glucose metabolism in mice and humans. Therefore, IFN? can be one of the critical mediators in the regulation of glucose metabolism through shaping microbiota. It is still unclear, however, if this mechanism is playing a role in diabetes. This project will: (1) Determine the role of IFN? and IFN?-dependent microbe A. muciniphila in a model of diet-induced obesity/diabetes using modulation of levels of IFN? and global analysis of pathways regulated by A. muciniphila in the gut. (2) Identify and test other microbes and microbial factors involved in regulation of glucose metabolism. For this, microbiota perturbation by antibiotics followed by global analyses of gut microbiome and host transcriptome combined with causal inference analysis will be employed. In addition to mouse model, public metagenomics data on T2D in humans will be used to establish a data resource matching mouse and human microbes and microbial genes potentially involved in glucose metabolism and T2D. (3) Test the role of microbiota in therapeutic effects of anti-diabetic drugs, specifically under treatment with metformin, a drug most frequently used in human T2D. This research will provide a mechanistic explanation of how intestinal immunity and changes in microbiota affect glucose metabolism and will help disclose mechanisms of T2D as well as will identify protective microbial factors for development of therapy of diabetes.